Shell-selective Ionisation and Fragmentation of Molecules using Soft X-rays

Inner shell ionization of molecules composed of low atomic number targets predominantly results in loss of electrons (as opposed to photon emission) through processes such as Auger or Coster-Kronig transitions, and autoionisation.  Such drastic changes in the electronic structure of the molecule leads to the formation of stable or unstable multiply charged molecular ions.  Depending on the details of the electron removal mechanism, the transient molecular ions species that are precursors to dissociation can be in a variety of states.  The dissociation patterns -- channels, branching ratios and kinematics of the fragments -- can be expected to reveal the details of the transition from a molecule to theseparated fragments -- provided that the correlated kinematics of theelectrons and ions are determined in the experiment, while also controlling the energy transfer to the molecule.  The talk will focus on the development of an apparatus capable of doing this, and a few results on dissociative photo-ionisation of CS_2 and OCS will be presented.